Thermally initiated pyrotechnic delay time fuze



Nov. 14, 1967 MCFANN ET AL 3,352,242

THERMALLY INITIATED PYROTECHNIC DELAY TIME FUZE Filed Nov. 29, 1965 CHARLES E. MCFANN LOUIS J. deSABLA I NVEN TORS ATTORNEYS United States Patent 3,352,242 THERMALLY INITIATED PYROTECHNIC DELAY TIME FUZE Charles E. McFanu, Woodbine, and Louis J. de Sabla, Silver Spring, Md, assignors to the United States of America as represented by the Secretary of the Navy Filed Nov. 29, 1963, Ser. No. 327,161 5 Claims. (Cl. 10285.6)

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates generally to fuze mechanisms, and more specifically to thermally-initiated, pyrotechnic-delay, time fuze mechanisms.

In the past, many mechanisms have been provided for actuating, after a predetermined time delay, the fuze mechanisms of rockets and various other projectiles. These mechanisms have generally been clockwork or timer types actuated by an inertial mass in response to the initial acceleration of the rocket or other projectile. While such prior art devices have been generally satisfactory, various difliculties have been encountered in their operation or use. The principal ditficulty has been occasioned by the need for providing a time delay fuze mechanism which will function satisfactorily and reliably when subjected to high accelerations and severe conditions of aerodynamic heating. Because of these environmental problems, the prior art fuze mechanisms have been extremely expensive to produce and have not provided the desired reliability under all conditions of use. Manifestly, it would be highly desirable to provide a time delay fuze mechanism which would reliably perform when exposed to the aforementioned environmental conditions and even utilize these inherent environmental conditions to good advantage.

It is therefore a primary object of the present invention to provide a time delay fuze mechanism which will be actuated by aerodynamic heating of the rocket or other projectile in which the fuze is utilized.

It is another object of this invention to provide a time delay fuze mechanism embodying a minimum number of moving parts to offset problems caused by high accelerations applied to the fuze mechanism.

It is a further object of this patent invention to provide a new and improved time delay fuze mechanism which is inexpensive to construct and easy to assemble.

With these and other objects in view, the present invention contemplates a hollow actuator housing adapted to be mounted snugly within a socket formed in the ogive of a rocket or other projectile and containing therein a springbiased firing pin. A plurality of detent balls are disposed in apertures in the housing and are maintained in this position by a segmented retaining ring and a thermal ring formed of a low melting point alloy. The detent balls engage a circumferential groove formed in the firing pin and retain it in a cocked position against the urging of the spring. Upon firing of the rocket and consequent aerodynamic heating of the ogive thereof, the thermal ring melts and releases the retaining ring and detent balls to enable the spring to drive the firing pin into initiating contact with a pyrotechnic-delay time fuze positioned adjacent the a-ctuator housing.

Other objects, advantages, and novel features of the invention will become readily apparent upon consideration of the following detailed description when read in conjunction with the accompanying drawings wherein:

FIG. 1 is a longitudinal sectional view of the ogive of the rocket having the time-delay fuze mechanism of the present invention mounted therein and illustrating the salient features thereof;

FIG. 2 is an enlarged sectional view taken along the line 22 of FIG. 1 and illustrates the detent ball arrangement for locking the firing pin in a cocked position; and

FIG. 3 is an enlarged sectional view taken along the line 3-3 of FIG. 1 and illustrates the flat surfaces formed on the actuator housing to provide void spaces into which the melted thermal ring can flow.

Attention now is directed to the drawings, wherein like numerals of reference designate like parts throughout the several views, and more particularly to FIG. 1 wherein a thermally-initiated, time-delay, fuze mechanism, desig nated generally by the reference numeral 10, is illustrated disposed within a coaxial socket 11 formed in the ogive 12 of a rocket. As shown, the fuze mechanism 10 is disposed wholly within the ogive in order to maintain unbroken the streamlined outer surface thereof. The fuze mechanism 10 comprises an actuator housing 14 and a firing pin 15 disposed within a cylindrical bore 16 formed in the housing. A compression spring 18 is interposed between the closed end of the housing 14 and the firing pin 15 and normally urges the firing pin to the right as viewed in FIG. 1.

A plurality of detent balls 19 are disposed within apertures 20 circumferentially spaced (FIG. 2) about the periphery of the reduced section of the housing 14. The

detent balls 19 project radially inward and into a circumferential groove 21 formed on the firing pin 15 and normally restrain the firing pin against the urging of thecompression spring 18. The detent balls 19 are normally retained within the apertures 20 by means of a segmented ring comprising segments 22 and 24. The segments 22 and 24 are in turn retained in the position shown in the drawings by meansof a thermal ring 25 formed of a low melt ing point alloy. Although it will be obvious that many alloys will meet this criteria, an alloy which has been found to be ideally suited to this application is a eutectic mixture vwhich contains by weight; 52% bismuth, 32% lead, and 16% tin. The outer periphery of the thermal ring 25 is so dimensioned as to be in intimate thermal con tact with the wall of the socket 11.

The exterior of the housing is provided with a plurality of flat surfaces 26 (FIG. 3) which, together with the adjacent walls of the socket 11, define a plurality of void spaces adjacent the thermal ring 25.

A pyrotechnic-delay, time fuze 28 is disposed within the ogive and has the initiating end thereof positioned adjacent the actuator housing 14 by means of a plastic cup 29. The pyrotechnic fuze 28 is conventional and comprises generally a pyrotechnic delay column and a detonator (not shown) which is operable upon initiation thereof to set off thebooster charge (not shown) of the rocket.

Operation In order that a better understanding of the invention might be had, its mode of operation will now be described. When a rocket carrying the fuze 10 is launched, aerodynamic heating causes the outer surface of the ogive to attain a relatively high temperature. As the heat penetrates to the inside of the ogive, the thermal ring 25 melts and flows, under the influence of acceleration and spin, into the void spaces defined by the surfaces 26 and the walls of the socket 11. Fusion of the thermal ring 25 releases the segments 22 and 24 and enables the energy stored in the compression spring 18 to move the firing pin 15 to the right as viewed in FIG. 1, camming the detent balls 19 outward against the segments 22 and 24 which in turn are forcedradially outward into the space previously'filled by the thermal ring 25. After the detent balls 19 have cleared -the major diameter of the firing pin 15, the remaining energy of the spring 18 drives the firing pin aft into initiating contact with the fuze 28, thereby initiating the time delay feature which will in turn initiate the booster charge of the rocket. In meteorological rockets, for example, detonation of the booster charge would result in the dispersal of metallic chaff or release of a metallized parachute which may then be tracked by radar to aid in ascertaining various meteorological information. In rockets intended for other than meteorological missions, initiation of the booster charge would of course perform other functions.

From the foregoing, it will be readily apparent that the present invention possesses numerous advantages not found in prior art devices. For example, aerodynamic heating of the ogive no longer produces detrimental effects, but is in fact utilized to advantage to initiate the operation of the fuze mechanism. Also, high acceleration is no longer a problem since the acceleration applied to the one moving part, i.e. the firing pin, is in the direction in which it normally moves to perform its function and thus supplements the action of the firing pin spring.

It is to be understood that the above-described arrangement merely constitutes a preferred embodiment of the present invention. Numerous modifications will readily occur to those skilled in the art which will provide a similar device still embodying the principles of the present invention and still falling within the spirit and scope thereof.

What is claimed is:

1. In combination with a rocket having an ogive, said ogive having an unbroken streamlined outer surface thereon and a coaxial socket therewithin, a thermally initiated fuze mechanism for said rocket comprising:

a hollow actuator housing having an open end and a closed end,

said housing being disposed in said socket,

a firing pin disposed within said housing,

a fuze disposed adjacent the open end of said housing,

resilient means interposed between said firing pin and the closed end of said housing and normally urging said firing pin toward said fuze,

means on said housing for restraining said firing pin against the urging of said resilient means,

said restraining means including a plurality of detent balls disposed in apertures circumferentially spaced about said housing,

said balls projecting radially inward of the inner surface of said housing and into a circumferential groove formed on said firing pin, and

thermal means on said housing completely surrounding said restraining means and responsive to aerodynamic heating of the ogive for releasing said restraining means whereby said resilient means will drive said firing pin into initiating contact with said fuze.

2. In combination with a rocket having an ogive, said ogive having an unbroken streamlined outer surface thereon and a coaxial socket therewithin, a thermally initiated fuze mechanism for said rocket comprising,

a hollow actuator housing having an open end and a closed end,

said housing being disposed in said socket,

a firing pin disposed within said housing,

a fuze disposed adjacent the open end of said housing,

resilient means interposed between said firing pin and the closed end of said housing and normally urging said firing pin toward said fuze,

means on said housing for restraining said firing pin against the urging of said resilient means,

said restraining means including a plurality of detent balls disposed in apertures circumferentially spaced about said housing,

said balls projecting radially inward of the inner surface of said housing and into a circumferential groove formed on said firing pin,

thermal means including a segmented ball retaining ring encompassing said housing in the plane of said balls, and

a thermal ring formed of a low melting point alloy encompassing said retaining ring and adapted to melt upon aerodynamic heating of the ogive whereby said detent balls and retaining ring segments may be cammed radially outward whereby said resilient means will drive said firing pin into initiating contact with said fuze.

3. A fuze mechanism as defined in claim 2 wherein said low melting point alloy is a eutectic mixture of bismuth, lead and tin in which the constituents are present in the following proportions by weight; 52%, 32% and 16%, respectively.

4. A fuze mechanism as defined in claim 2 wherein said housing is provided with flat sections adjacent said thermal ring and spaced from the walls of the socket to define void spaces into which the melted alloy may flow.

5. In combination with a rocket having an ogive having an unbroken streamlined outer surface thereon and a coaxial cylindrical socket therewithin, a thermally initiated fuze mechanism for said rocket comprising:

a hollow cylindrical actuator housing having open and closed ends and a plurality of flat surfaces circumferentially spaced about the exterior periphery thereof.

said housing being disposed in said cylindrical socket and in intimate thermal contact therewith,

a cylindrical firing pin slidably disposed within said housing,

said firing pin being provided with a circumferential groove having tapered side walls and spaced substantially equidistant from the ends thereof,

a pyrotechnic delay time fuze disposed adjacent the open end of said housing,

a compression spring interposed between said firing pin and the closed end of said housing and normally urging said firing pin toward said fuze,

a plurality of detent balls disposed in apertures circumferentially spaced about said housing in a plane adjacent the plane of said flat surfaces,

said detent balls projecting radially inward of the inner surface of said housing and into the circumferential groove formed in said firing pin and normally restraining said firing pin against the urging of said p a segmented ball retaining ring encompassing said housing in the plane of said balls, and

a thermal ring encompassing said retaining ring and adapted to melt upon aerodynamic heating of the ogive and flow into the void spaces defined by said flat surfaces and the walls of the socket whereby said detent balls and retaining ring segments may be cammed radially outward to release said firing pin and enable said compression spring to drive said firing pin into initiating contact with said fuze,

said thermal ring comprising an eutectic mixture by weight of bismuth 52%, lead 32% and tin 16%.

References Cited UNITED STATES PATENTS 1,453,091 4/ 1923 Delbare 1692,8 2,465,009 3/ 1949 Chase 102-82 X 3,007,412 11/1961 Kipfer 10271 3,008,414 1l/1961 Jasse 102--85 X 2,091,589 8/1937 Finzi 16928 2,850,978 9/ 1958 Franklin 102-70.2

FOREIGN PATENTS 233,097 5/ 1925 Great Britain.

SAMUEL W. ENGLE, Primary Examiner.

SAMUEL FEINBERG, BENJAMIN A. BORCHELT,

Examiners.

G. L. PETERSON, G. H. GLANZMAN,

Assistant Examiners. 

1. IN COMBINATION WITH A ROCKET HAVING AN OGIVE, SAID OGIVE HAVING AN UNBROKEN STREAMLINED OUTER SURFACE THEREON AND A COAXIAL SOCKET THEREWITHIN, A THERMALLY INITIATED FUZE MECHANISM FOR SAID SOCKET COMPRISING: A HOLLOW ACTUATOR HAVING AN OPEN END AND A CLOSED END, SAID HOUSING BEING DISPOSED IN SAID SOCKET, A FIRING PIN DISPOSED WITHIN SAID HOUSING, A FUZE DISPOSED ADJACENT THE OPEN END OF SAID HOUSING, RESILIENT MEANS INTERPOSED BETWEEN SAID FIRING PIN AND THE CLOSED END OF SAID HOUSING AND NORMALLY URGING SAID FIRING PIN TOWARD SAID FUZE, MEANS ON SAID HOUSING FOR RESTRAINING SAID FIRING PIN AGAINST THE URGING OF SAID RESILIENT MEANS, SAID RESTRAINING MEANS INCLUDING A PLURALITY OF DETENT BALLS DISPOSED IN APERTURES CIRCUMFERENTIALLY SPACED ABOUT SAID HOUSING, SAID BALLS PROJECTING RADIALLY INWARD OF THE INNER SURFACE OF SAID HOUSING AND INTO A CIRCUMFERENTIAL GROOVE FORMED ON SAID FIRING PIN, AND THERMAL MEANS ON SAID HOUSING COMPLETELY SURROUNDING SAID RESTRAINING MEANS AND RESPONSIVE TO AERODYNAMIC HEATING OF THE OGIVE FOR RELEASING SAID RESTRAINING MEANS WHEREBY SAID RESILIENT MEANS WILL DRIVE SAID FIRING PIN INTO INITIATING CONTACT WITH SAID FUZE. 